As is evident from the name, the district of East Garo Hils is a hilly terrain. The hills are highly dissected and one major formation is the Arbella Range, which is cuts through the south-central part of the district. The range consists of peaks with an average height of 700 metres above sea level. Another important physiographic feature is the Simsang Valley which runs through the southern part of the district. The River Simsang is the longest river in Garo Hills, which originates in West Garo Hills and flows through East Garo Hills and thence to South Garo Hills. The topography of the rest of the district is of undulating low hills, with altitude ranging from 150 to 600 netres above sea level. Besides the Simsang (Someshwari), the district is also drained by the rivers Manda (Dudhnoi) & Damring (Krishnoi), which have their sources within the district. Other than the Simsang which drains southeastwards, the others all runs north or northwest towards the Brahmaputra.
The district is mainly drained by perineal & non-perennial streams and the drainage system of the district comprises of the following:
1. The Simsang (Someshwari) & its tributaries: The Simsang flows in from the neighbouring district of West Garo Hills, where its source is, it flows eastwards and then southwards within East Garo Hills and then flows out to neighboutring South Garo Hills, and thence to Bangladesh. The Simsang and its tributaries drains more than 50% of the district.
2. The Damring (Krishnai) & its tributaries: The Damring has its source in East Garo Hills and it flows northwards to neighbouring North Garo Hills, and then to Assam and drains to the Brahmaputra.
3. The Manda (Dudhnoi) & its tributaries: The Manda has its source in East Garo Hills and it flows northwards to neighbouring North Garo Hills, and then to Assam and drains to the Brahmaputra.
Seismically, East Garo Hills district lies in in Zone V. Nearly all of the state of Meghalaya, lies on the "Shillong Massif". This is a block-like structure that has not undergone much folding or faulting as compared to the surrounding areas. The main threats to the state come from faults bounding the massif with the surrounding areas. The northern part of the massif has several faults, among the newly identified Oldham Fault that is believed responsible for the 1897 earthquake. The southern boundary is marked by the east-west trending Dauki Fault, along the Bangladesh border. Moderate earthquakes have occurred in this state but the most significant of all was the Great Assam earthquake of 1897. Centred across the state border in Assam, much of Meghalaya was severely jolted.
The Largest Instrumented Earthquake in Meghalaya was on 7 April 1951 - 6.8 (TS) 20:29:12.40 UTC, 25.80N, 90.40E near Rongrenggre, which is a suburb of Williamnagar, the district headquarters of East Garo Hills.